The metathesis reaction operates a redistribution of the alkylidene groups between olefins. It is particularly advantageous, for example, for restoring a balanced proportion between light olefins obtained by steam-cracking: ethylene, propylene and butenes.
Several types of catalysts are known as being capable to catalyze this reaction. They are either of the homogeneous type, when their constituting elements are all soluble in the reaction medium, or of the heterogeneous type, when at least one of the elements is insoluble in said medium. The latter are particularly advantageous when the active metal is costly and must accordingly be re-used without losses. Rhenium-containing catalysts are of this type. Their use in heterogeneous form has been recommended for catalyzing methathesis of simple olefins, for example in U.S. Pat. Nos. 3 641 189 and 3 676 520.